Perfluoropolyethers are highly regarded in the specialty lubricant field because of their wide liquid ranges, low vapor pressures and high thermal and oxidative stabilities. Because of these properties, (many of which are unique to fluorocarbons) they are excellent high performance lubricants, superior base stocks for greases, excellent lubricating oils, and heat transfer fluids. In addition, because of these uniquely outstanding properties, saturated perfluoropolyethers are of current interest as specialty sealants, elastomers and plastics.
In spite of their unlimited potential, only three perfluoropolyethers are commercially available to date because of the lack of fluorocarbon intermediates which are suitable for preparing the polymers. They are
1. DuPont's Krytox.TM. fluid which is made by polymerizing hexafluoropropylene oxide; PA1 2. Demnum.TM. fluid, a product of Daikin, is obtained by ring opening polymerization of 2,2,3,3-tetrafluorooxetane using a catalyst with subsequent treatment of the highly fluorinated polyether with fluorine gas to give a perfluorinated product; and PA1 3. Monticatini Edison's Fomblin Z.TM. and Fomblin Y.TM. fluids which are prepared by photooxidizing tetrafluoroethylene and hexafluoropropylene oxide, respectively, in the presence of oxygen. PA1 2,2-dimethoxypropane, 2,2-dimethoxybutane, PA1 2,2-dimethoxypentane, 2,2-dimethoxyhexane, PA1 3,3-dimethoxypentane, 3,3-dimethoxyhexane as well as the diethoxy, dipropoxy, dibutoxy and diphenoxy analogues of the previously mentioned ketals.
A process has been described for preparing perfluoropolyethers by reaction of a hydrocarbon polyether with elemental fluorine in the presence of a hydrogen fluoride scavenger. See U.S. Pat. No. 4,755,567.